The present invention relates to an image signal interface system for use between an image signal source and an image output device, and more particularly to an image interface system which, when hard copies are to be produced by an image output device in response to image signals generated by a plurality of image signal sources having different .gamma. characteristics, converts the image signals from the image signal sources to image signals that match the .gamma. characteristics of the image signal sources, and which, when analog image signals are generated by the image signal sources, converts the analog signals to digital image signals based on analog image signal attribute data which have been preset depending on the type of the image signal sources.
Medical image diagnostic apparatus such as CT scanners or the like allow localized regions of human bodies to be displayed as image information so that such localized body regions can clearly be viewed for medical analysis and diagnosis by doctors or the like. CT scanners or the like display image information on CRTs or the like to permit doctors to make medical diagnosis based on the displayed images. The image information displayed on the CRTs may be exposed to and recorded on photographic mediums and kept as hard copies, which can be used for medical diagnosis at any time and place. An image signal produced by an image signal source such as a CT scanner and representing such image information is usually applied as an analog video signal, i.e., an analog image signal, to an image output device such as a laser beam printer or the like, in which the analog video signal is converted to exposure data and recorded on a photosensitive medium.
The image output device may be supplied with analog image signals from various medical image diagnostic apparatus such as a CT scanner, an ultrasonic imaging apparatus, a nuclear magnetic resonance imaging apparatus, and the like which have been developed and used with the progress of medical diagnostic technology. Analog signals generated by these different medical image diagnostic apparatus may have different attributes such as a sampling frequency, a horizontal signal input period, a vertical signal input period, etc. Therefore, the image output device must produce exposure data while taking into account these attributes of the analog image signals.
One conventional image output device includes a plurality of converters designed for converting analog signals of different attributes, the converters being selectively connectable to the image signal source which is actually used. This arrangement is however complex. If a new image signal source of another kind is to be connected, a new converter which matches the new image signal source has to be added to the image output device. Accordingly, the image output device may be highly expensive.
According to another prior image output device, the conversion characteristics of a converter which converts an analog image signal to exposure data are set by DIP switches depending on the attributes of an analog image signal to be applied. However, it is highly tedious and time-consuming for the operator to shift the DIP switches, and the image output device is virtually difficult to adapt itself to use in connection with many types of image signal sources.
The medical image diagnostic apparatus such as a CT scanner, an ultrasonic imaging apparatus, and a nuclear magnetic resonance imaging apparatus, normally apply image signals to CRTs to display images for diagnosis. In order to display such images, digital image signals are converted to analog video signals before they are supplied to the CRTs.
When an image signal (analog video signal) is supplied from a medical image diagnostic apparatus to an image output device to produce a hard copy, the conversion characteristics (.gamma. characteristics) with which a digital image signal is to be converted to an analog video signal in the medical image diagnostic apparatus may not match the .gamma. characteristics of the image output device. If such a .gamma. characteristics mismatch exists, an image recorded on a photo-sensitive medium and reproduced as a hard copy is unclear and cannot be used for accurate medical diagnosis. Medical image diagnostic apparatus have different .gamma. characteristics, respectively.
It may be possible to provide a plurality of image output devices having different .gamma. characteristics, and one of such image output devices may be selected for use with a medical image diagnostic apparatus used so that their .gamma. characteristics are matched. This proposal is not economical and requires a large installation space for the plural image output devices.
The .gamma. characteristics of an image output device may be adjusted to match those of a medical image diagnostic apparatus in use. Such an adjusting procedure usually requires a highly skilled operator, and is tedious and time-consuming. Therefore, it cannot meet a basic demand in the medical field for quick diagnosis.